\chapter{Conclusions}
\label{ch:conclusions}
In this project we have studied the evolution of RSSI and LQI values over the distance. In theory it is possible to derive the distance from the path loss of the signal. This study has been carried out in three different scenarios with different platforms (Telosb and ASEBAN).

The empirical results for RSSI readings have been compared with the Path Loss Propagation model. This model has been adapted through curve fitting in order to predict the signal decay in different scenarios (outdoor and indoor) using the CC2420.

The indoor measurements showed a good correlation between path loss model and RSSI values up to 20 meters. Beyond this limit the RSSI value became unstable and poorly modeled by the theoretical expression. The outdoor measurements showed a more reliable behavior up to 100 meters. The path loss propagation model was successfully adapted, fitting the obtained results. This model was used later on in the positioning experiments. Other parties have performed similar experiments with similar results. 

Based on the outdoor model developed after empirical studies, basic positioning experiments were carried out. Trilateration was used to obtain the position of a mote in a $49\ \textrm{m}^2$ grid. The test setup used three anchors from which the RSSI values were retrieved by a moving mote. We were able to obtain a correct position with an average error of 2 meters approximately.

LQI values are not useful for direct positioning but they may be used to increase the reliability of the RSSI measurements.

In line with the experiments done by other parties we can conclude that we are able to obtain a distance between two nodes by obtaining the RSSI value and we are able to use this for simple positioning.

\begin{figure}[!c]
  \centering
  \includegraphics[width=15cm]{kids_helping_out.jpg}
  \label{fig:smallHelpers}
  \caption{Thanks goes out to our small helpers}
\end{figure}
